It's the attack of the 50-foot Vulcan! Spock gets yuuuuuuuuuuge in Walter Koenig's sole contribution to the animated series, as the TOS Rewatch encounters "The Infinite Vulcan."
This is a very ambitious episode, with a lot of really nifty ideas, and some rather heavy plot elements. It’s pretty impressive for a 1970s Saturday morning cartoon to show us a room full of corpses, though the censors probably didn’t blink because they were plants. The notion of sentient ambulatory plants is a fun one, though not as much is done with it as one might hope, and the design is nicely alien, continuing the work the animated series has done from jump in giving us truly alien designs. And given that Spock has been regularly shown to be a kind of superman, the idea that Keniclius views him as a perfect base for a clone army of telepathic soldiers with the strength of a Vulcan and the passion of a human is actually a really clever extrapolation of how Spock has been portrayed. I like that the script acknowledges something that Star Trek in general has ignored repeatedly, which is the very real possibility of bacterial contamination of the strange new worlds they visit. And it’s good to see so much contributed to the story by Uhura and especially Sulu. (The ending cracks me up every time, though I could live without the oh-so-70s wink at the camera.)